Cracking catalysts which are used to crack hydrocarbon feedstocks become relatively inactive due to the deposition of carbonaceous deposits on the catalyst. These carbonaceous deposits are commonly called coke. After the cracking step, the catalyst passes to a stripping zone where steam is used to remove strippable hydrocarbons from the catalyst. The catalyst then goes to the regenerator, where the catalyst is regenerated by burning the coke in an oxygen-containing gas. This converts the carbon and hydrogen in the coke to carbon monoxide, carbon dioxide and water.
Oxidation catalysts are currently being used in fluid catalytic cracking (FCC) combustion units to oxidize CO to CO.sub.2 in the catalyst bed during the coke-burning step in the regenerator. Typically the oxidation catalysts are particulate combustion additives that contain 100 to 1000 ppm Pt and/or Pd supported on alumina. The combustion additives are mixed with FCC catalysts in amounts that provide a Pt/Pd content of about 0.1 to 2 ppm and preferably about 0.1 to 0.8 ppm. The oxidation of CO to CO.sub.2 in the catalyst bed yields many benefits. One benefit is the reduction of CO emissions. Another is the avoidance of "after-burning", i.e., the oxidation of CO to CO.sub.2 outside the catalyst bed, which results in a loss of heat energy and causes damage to the cyclones and flue gas exit lines. The major benefit in using oxidation catalysts to oxidize CO to CO.sub.2 in the catalyst regenerator bed derives from the heat released when the CO is oxidized to CO.sub.2. This heat raises the catalyst bed temperature and thereby increases the coke-burning rate. This gives a lower residual carbon level on the regenerated catalyst. This, in turn, makes the regenerated catalyst more active for the cracking step. This increases the amount of useful products produced in the FCC unit.
CO oxidation catalysts (also referred to herein as agents, additives, promoters, compositions, etc.) when intended for use in FCC units, must of course be compatible under the actual conditions used in FCC units and must remain effective for their subsequent function in the regeneration step. Such FCC units conventionally require temperatures of 800.degree.-1000.degree. F. (427.degree.-538.degree. C.) and catalyst residence times of 3 to 15 seconds in the reducing atmosphere of the reactor; followed by temperatures of 800.degree.-1000.degree. F. (427.degree.-538.degree. C.) in the steam atmosphere of the stripper and temperatures of 1100.degree.-1400.degree. F. (593.degree.-760.degree. C.) and catalyst residence times of 5 to 15 minutes in the oxidizing atmosphere of the regenerator. Additionally, CO oxidation agents for use in FCC units must be effective in the presence of the materials present in FCC units, such as cracking catalysts of various compositions and oil feedstocks of various compositions and their cracked products. My novel CO oxidation agents are useful in and compatible with all these FCC conditions.